Add is_container and nqp_decontainerize ops.

src/ops/nqp.ops

@@ -963,3 +963,61 @@ inline op repr_get_primitive_type_spec(out INT, in PMC) :base_core {
         $1 = STORAGE_SPEC_BP_NONE;
     }
 }
+
+/*
+
+=item is_container
+
+Checks if the type of thing in $2 is a container or not. Puts a non-zero
+value in $1 if it is a container and 0 otherwise. Any non-6model type is
+considered not to be a container.
+
+=cut
+
+*/
+inline op is_container(out INT, in PMC) :base_core {
+    if ($2->vtable->base_type == smo_id)
+        $1 = STABLE($2)->container_spec != NULL;
+    else
+        $1 = 0;
+}
+
+/*
+
+=item nqp_decontainerize
+
+If the thing in $2 is a container, does a decontainerizing operation
+and puts the contained value in $1.
+
+=cut
+
+*/
+inline op nqp_decontainerize(out PMC, in PMC) :base_core {
+    if ($2->vtable->base_type == smo_id) {
+        ContainerSpec *spec = STABLE($2)->container_spec;
+        if (spec) {
+            if (!PMC_IS_NULL(spec->value_slot.class_handle)) {
+                /* Just get slot. */
+                $2 = VTABLE_get_attr_keyed(interp, $2, spec->value_slot.class_handle,
+                    spec->value_slot.attr_name);
+            }
+            else {
+                /* Invoke FETCH method. */
+                PMC *old_ctx = Parrot_pcc_get_signature(interp, CURRENT_CONTEXT(interp));
+                PMC *meth    = VTABLE_find_method(interp, $2, Parrot_str_new(interp, "FETCH", 0));
+                PMC *cappy   = Parrot_pmc_new(interp, enum_class_CallContext);
+                VTABLE_push_pmc(interp, cappy, $2);
+                Parrot_pcc_invoke_from_sig_object(interp, meth, cappy);
+                cappy = Parrot_pcc_get_signature(interp, CURRENT_CONTEXT(interp));
+                Parrot_pcc_set_signature(interp, CURRENT_CONTEXT(interp), old_ctx);
+                $1 = VTABLE_get_pmc_keyed_int(interp, cappy, 0);
+            }
+        }
+        else {
+            $1 = $2;
+        }
+    }
+    else {
+        $1 = $2;
+    }
+}